Fig. 2. Ihh signaling is not required for Hh target gene expression in the retina and optic nerve. (A-E) Gli and (F) Pax2 transcripts detected by in situ hybridization in sections through the developing eye and optic nerve of E14 wild-type (A,B) and Ihh^-/- (D-F) embryos, and E15 ThyCreShh^n/c embryos (C). (A,B,D-F) Horizontal sections. (C) Frontal section. Compared with wild type (A,B), Gli expression is specifically lost in the peri-ocular mesenchyme of Ihh^-/- mice (D,E) and in the retinal neuroblast layer of ThyCreShh^n/c embryos (C). Arrowheads (A,C,D) indicate Gli-expressing cells adjacent to the retinal pigment epithelium. Astrocyte precursor cells in the optic nerve and at the optic disc develop normally in Ihh^-/--mutant embryos, as indicated by normal Pax2 expression (F).